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For the past year, my 2010 Hyundai Tucson has intermittently (1-2 times a month) had "hesitation" problems where pressing the accelerator doesn't increase the RPMs - usually within 2 minutes of starting the engine cold. On 3 occasions though, the engine has died and merely wouldn't restart - only to restart several hours later or the next day as if nothing was ever wrong. During this time though, I can spray carb cleaner into the intake, and it fires up while the carb cleaner is present only to die again a few seconds later.

I've replaced the fuel filter, fuel pump, throttle position sensor, mass air flow sensor, and engine pressure regulator already. I've also taken apart the injection system, cleaned it, and put it back together again. It is still happening.

My next best guess is the fuel injectors, but I'd love some other opinions or thoughts about what I could/should check before spending all the money on brand new injectors. Would appreciate any ideas you can provide!

  • Welcome! Interesting question you have there… Mostly I do diesel, but it seems odd to me that all of the injectors would be failing or clogging at the same time. Seems more likely that there is a common element "upstream" that is the culprit. You test with the carb cleaner suggests that the problem is fuel – I'd start by looking for something common, maybe a bad ground, related to the injectors. – dlu Dec 22 '16 at 4:29
  • Good idea - I haven't checked any of the electrical system on it yet - will take a while to figure out where it is going, it all goes directly into the wiring harness and off to god-knows-where. – Jeff Dec 22 '16 at 5:21
  • There are probably connectors at the injectors, no? If you can "back probe" them – find a way to get the meter probes to reach the connectors while they are still connected to the injectors – it might not be too hard to figure out what is happening. – dlu Dec 22 '16 at 5:24
  • This might be helpful: 2carpros.com/articles/how-to-test-a-fuel-injector – dlu Dec 22 '16 at 5:38
  • I was looking for something just like this, thanks! All I ran across elsewhere was the "screwdriver" test which just seemed a little too easy to miss something or think I'm hearing something I'm not. I"ll run through these troubleshooting tips tomorrow on my car :-) – Jeff Dec 22 '16 at 7:10
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This sounds like the fuel pump is failing. The only way to tell for sure is to put a fuel pressure gauge on the fuel rail and test it when it's behaving as such. If the fuel pump heats up and doesn't want to pump fuel anymore, it will cause the issues you are talking about. It can be intermittent. If it is the fuel pump, you can expect it will completely go out at some point when you least expect it and you need the vehicle the most (Murphy's Law applies here, I think).

  • He's already replaced the fuel pump – Zaid Dec 22 '16 at 15:16
  • @Zaid - It has to fuel related. Injectors don't fail like this. Even a new pump can fail. Seems to me it would either be the pump or it could be power to the fuel pump. – Pᴀᴜʟsᴛᴇʀ2 Dec 22 '16 at 15:22
  • Have you ruled out an issue on the air side? A sticky IAC, perhaps? – Zaid Dec 22 '16 at 15:23
  • I replaced the fuel pump after the last time it died completely, and it hasn't done that in a few months now. But I still get the hesitation. The main problem is my inability to troubleshoot during the infrequent times I get a problem. But the fuel pump, fuel filter, and fuel relay switch have all been replaced and I still get the hesitations. Would be odd to have the same infrequent problem with two pumps. Haven't ruled out anything really though. Could be a small, infrequent vacuum leak too I think. – Jeff Dec 23 '16 at 4:11

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